Hitherto, halogen compounds have generally been used for making polyolefins flame-retardant. However, recently because of the toxicity of halogen compounds, use of them is essentially prohibited in European countries.
Under the above described situation, non-halogen flame retardants containing metal hydroxides such as magnesium hydroxide, aluminium hydroxide or the like have variously been investigated for the purpose of making polyolefins flame-retardant without use of halogen-containing flame retardants.
However, addition of metal hydroxides to polyolefins involves a problem that the flame-retarding property of them is not always satisfactory even though an extremely large amount of metal hydroxide is added thereto and that the mechanical strength and moldability of polyolefins containing such a large amount of metal hydroxides would often decrease. Even though glass fibers are added to polyolefins, the fame-retarding property of them is not always improved. Further, even though antimony trioxide is added to polyolefins, the flame-retarding property of polyolefins is not always sufficient.
In order to reduce the amount of metal hydroxides to be added to polyolefins, there is known a method of using red phosphorus. However, red phosphorus generates a bad smell during use and additionally involves a safety problem.